net/tap: set locally administered bit for fixed MAC address

[ upstream commit c3006be2acab49c6b77ae9c9ef04b061e5dacbd6 ]

When the tap driver is loaded and the user selects the optional
"mac=fixed" setting, the tap driver incorrectly uses a globally
unique EUI-48 identifier (as documented in RFC 7042) of
00:64:74:61:70:<iface_idx>. Since this is a locally generated ID,
the Local bit in the MAC address should be set to 1, resulting in
the new address 02:64:74:61:70:<iface_idx>.

Bugzilla ID: 1198
Fixes: f692178 ("net/tap: add support for fixed MAC addresses")

Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Ferruh Yigit <ferruh.yigit@amd.com>

doc/guides/nics/tap.rst

@@ -34,14 +34,14 @@ Using the option ``mac=fixed`` you can create a fixed known MAC address::
 
 The MAC address will have a fixed value with the last octet incrementing by one
 for each interface string containing ``mac=fixed``. The MAC address is formatted
-as 00:'d':'t':'a':'p':[00-FF]. Convert the characters to hex and you get the
-actual MAC address: ``00:64:74:61:70:[00-FF]``.
+as 02:'d':'t':'a':'p':[00-FF]. Convert the characters to hex and you get the
+actual MAC address: ``02:64:74:61:70:[00-FF]``.
 
-   --vdev=net_tap0,mac="00:64:74:61:70:11"
+   --vdev=net_tap0,mac="02:64:74:61:70:11"
 
 The MAC address will have a user value passed as string. The MAC address is in
 format with delimiter ``:``. The string is byte converted to hex and you get
-the actual MAC address: ``00:64:74:61:70:11``.
+the actual MAC address: ``02:64:74:61:70:11``.
 
 It is possible to specify a remote netdevice to capture packets from by adding
 ``remote=foo1``, for example::

drivers/net/tap/rte_eth_tap.c

@@ -2275,8 +2275,8 @@ set_mac_type(const char *key __rte_unused,
 	if (!strncasecmp(ETH_TAP_MAC_FIXED, value, strlen(ETH_TAP_MAC_FIXED))) {
 		static int iface_idx;
 
-		/* fixed mac = 00:64:74:61:70:<iface_idx> */
-		memcpy((char *)user_mac->addr_bytes, "\0dtap",
+		/* fixed mac = 02:64:74:61:70:<iface_idx> */
+		memcpy((char *)user_mac->addr_bytes, "\002dtap",
 			RTE_ETHER_ADDR_LEN);
 		user_mac->addr_bytes[RTE_ETHER_ADDR_LEN - 1] =
 			iface_idx++ + '0';